Physical Science Rocks and Minerals. Rocks Igneous rocks – Formed by the cooling and crystallization of hot molten rock called magma Igneous means – formed.

Physical Science

Rocks and Minerals

RocksIgneous rocks –

• Formed by the cooling and crystallization of hot molten rock called magma

• Igneous means – formed by fire

• 95% of the earth crust are igneous rocks

• examples include basalt and granite

From yahoo images

Rocks

Sedimentary rocks – • Formed by weatherd

material carried by water, wind or ice.• Most common rock in the upper part

of the earth’s crust• They cover 2/3 of earths surface.• Examples include sandstone, shale

and limestone

From yahoo images

Rocks

Metamorphic rocks –

• Formed from pre-existing rocks that are transformed under high

• temperature and pressure.

• Metamorphic means – changed in form

• Examples include marble, slate and diamond

From yahoo images

Minerals

• Minerals – The building blocks of rocks.

• Minerals are naturally formed, generally inorganic crystalline solid composed of an ordered array of atoms having a specific composition.

• Minerals differ from one another in their combination and proportion of elements and internal arrangement of atoms.

Classifying Minerals

• Crystal form – shape of crystal structure.

Classifying Minerals

• Crystal form – shape of crystal structure.

Classifying Minerals

• Polymorph – mineral composed of the same atom but have different crystal structure.

Classifying MineralsMohs Hardness Scale

Hardness is measured on the Mohs Scale, identified numerically hardness of by standard minerals, from 1 (softest) to 10 (hardest):

1. Talc 2. Gypsum 3. Clacite 4. Fluorite 5. Apatite 6. Orthoclase 7. Quartz 8. Topaz 9. Corundum 10.Diamond

• A mineral of a given hardenss will scratch a mineral of a lower number. With a systematic approach, you can use minerals of known hardness to determine the relative hardness of any other mineral.

Classifying Minerals

• Cleavage – tendency of a mineral to break along planes of weakness.

• Fracture – break that is not along the lines of a cleavage plane

From yahoo images

Classifying Minerals

• Luster – appearance of its surface as it reflects light

• Luster is independent of color

From yahoo images

Classifying Luster of Minerals• Adamantine - very gemmy crystals • Dull - just a non-reflective surface of any kind • Earthy - the look of dirt or dried mud • Fibrous - the look of fibers • Greasy - the look of grease • Gumdrop - the look a sucked on hard candy • Metallic - the look of metals • Pearly - the look of a pearl • Pitchy - the look of tar • Resinous - the look of resins such as dried glue or chewing

gum • Silky - the look of silk, similar to fibrous but more compact • Submetallic - a poor metallic luster, opaque but reflecting little

light • Vitreous - the most common luster, it simply means the look of

glass • Waxy - the look of wax

Classifying Minerals

• Color – is usually a poor way to judge minerals – the same mineral may exhibit a variety of colors

• Streak – color or mineral in its powder form. Usually obtained by rubbing across a porcelain plate.

From yahoo images

Classifying Minerals

• Specific Gravity – Density like measurement based on a comparison with the density of water.

From yahoo images

Classifying Minerals

• Chemical properties – fiz test – add HCl to carbonates and it will fizz

Makeup of Rocks and Minerals

• 118 know elements

• 88 are naturally occurring

• These combine to make 3400 different minerals

• About two dozen minerals are abundant

• These are made from 8 elements

Makeup of Rocks and Minerals

Makeup of Rocks and Minerals

• These 8 elements make up 98 % of the mass of the crust

• Half of this mass is due to O alone

• These minerals are broken into groups – silicates

oxides & carbonates

sulfides & sulfates

Building blocks of rock forming minerals

• Silicates – silicon with oxygen – SiO4

Building blocks of rock forming minerals

• Silicates – silicon with oxygen – SiO4

Oxides and Carbonates

• Oxides – metals combined with oxygen

Iron (hematite-magnetite) chromium (chromitite) manganese (pyrolusite) tin (cassiterite) uraninum (uraninite)

• Most metals come from these ores

Hemetite From yahoo images

Oxides and Carbonates

• Carbonates – minerals composed of carbonate ion CO3

Calcite – calcium carbonate CaCO3

Dolomite – calcium and magnesium carbonate CaMg(CO3)2

These two make up limestone calcite From yahoo images

Sulfides and Sulfates

minerals composed of sulfur S and

Sulfate SO42-

• Pyrite – fools gold FeS2

• Gypsum – calcium sulfate CaSO4

pyrite From yahoo images